Abstract: An insulated section is a contact surface opposite a car and is provided to extend along the side of a car and is connected to both train car cables in contact with the pantograph of the car. The contact surface has grooves formed from the upper edge to the lower edge in the vertical direction that is perpendicular to the traveling direction. The grooves are characterized by being formed in such a way that the cross section in the vertical direction forms part of the vertical direction of the contact surface at any position in the traveling direction.